A “high-altitude balloon” is a balloon, manned or unmanned, that can be released at ground level (or higher) and that climbs into the troposphere, stratosphere, or mesosphere at altitudes up to about 80 kilometers 50 miles). These balloons are filled with a lifting gas or with air at a temperature higher than that of the surrounding atmosphere.
High-altitude balloons often comprise two or more “gores” attached to each other. A “gore” is a tapering or triangular sector of a curved surface, such as the typical tapering panels of a parachute, beach ball, or conventional plastic-film high-altitude balloon. Gored balloons are formed by carefully cutting and connecting gores to form the balloon body, also known as the balloon envelope. Gores for these balloons are cut from rolls of film such as blown-extruded or cast-extruded plastic.
Gored balloons are fabricated on tables that are as long as the desired height of the balloon. Balloon film is dispensed from a roll at one end of the table and pulled, in some instances manually and in others with power assist, along the length of the table. For example, a balloon with an uninflated height of 30 meters (about 98 feet) requires a table of the same length. This in turn requires an indoor workspace at least that long. A table 60 meters 196 feet) long would be needed to fabricate a 60-meter balloon. Buildings that have been built for the purpose of making these balloons can be hundreds of feet long with no internal support posts or walls where the tables are located. Buildings that are not purpose-built are often not suitable.
After two or more gores have been laid out on a table, the balloon film must be tensioned. This can be done manually by pulling on the gores as they enter the sealing zone, or the entire lengths may be tensioned by taping or clamping them to the table. After the gores have been tensioned they may be heat sealed together by a traveling heat-seal head such as a track-controlled traveling band sealer or an overhead traveling impulse sealer.